Many types of medication are provided by syringes using needles which puncture a patient's skin or epidermis in order to inject the medication into the patient. Although commonly used, syringes have many drawbacks, such as deep structure injury due to the lacerating tip of the needle, possibilities of infection from contaminated needles, disposal problems and patients having a strong aversion to needles. Accordingly, there exists a need for alternative methods of delivering medication to patients.
Alternative methods of delivering medication have been developed. One known method is to deliver medication using a needleless injector. A needleless injector delivers medication by providing a strong, high pressure blast of the medication through a small orifice, which causes a minute stream of the medication to exit the orifice at a high rate of speed, thereby allowing the medication to penetrate into the skin and subcutaneous tissues. Although in use for many years, needleless injectors are not as prevalently used as syringes, due to, among other reasons, problems associated with the resistance of the skin which inhibits adequate delivery of medication.
The present invention is directed to an improved needless injector having, inter alia, an improved discharge mechanism and orifice structure which provide a more even distribution and higher velocity jet which dispenses the selected volume in a shorter time period. A higher velocity jet allows the injector to be used for administering any drug intermuscularly. Additional benefits, such as reduced force required to dispense liquid and easier tension setting or cocking of the spring are also provided. The present invention also provides an improved design which is less susceptible to leakage, less costly to manufacture and easier to maintain than prior art needless injectors.